Scenes of Mumbai Carnage and Chaos

The attackers arrived by boat on Nov. 26, 2008, carrying grenades and automatic weapons, and fanned out to hit multiple targets, a crowded train station, a Jewish center and the landmark Taj Mahal Hotel. TV cameras captured much of the three-day rampage live.

Before Leinenweber imposed the sentence, a victim shot in the attack gave emotional testimony during the morning hearing. Linda Ragsdale, a Tennessee children's author, spoke through tears describing how she lost friends in the attacks and her own injuries. She said she was haunted by the sounds of people suffering and her recovery from the wounds continues.

"I know what a bullet can do to every part of the human body," she said. "I know the sound of life leaving a 13-year-old child. These are things I never needed to know, never needed to experience."

The attack heightened the strain in a historically antagonistic relationship between India and Pakistan, which have fought three major wars. Indian officials accuse Pakistani intelligence of helping to plan the assault -- an allegation Pakistan denies.

The maximum sentence Headley, 52, faced Thursday was life in prison. He agreed to cooperate and plead guilty in 2010 to 12 counts to avoid what would have been his maximum sentence: death. He also secured a promise not to be extradited to India.

"The damage that was done was just unfathomable," the judge said. "Mr. Headley is a terrorist."

But no matter the sentence, said Leinenweber, "it's not going to deter terrorists. Terrorists don't care what happens to them."

Citing what they described as valuable intelligence Headley provided authorities about terrorist networks since his arrest, prosecutors had asked for a relatively lenient sentence of between 30 and 35 years.

The charges included conspiracy to aid the Pakistani-based group, Lashkar-e-Taiba, or the Army of the Pure, that mounted the attacks, as well as conspiracy to commit murder in India, and aiding and abetting in the murder of six Americans.